Electricity Generation

It seems inevitable that by 2020 coal will still be the basis of much electricity generation, worldwide. This is because some countries have large reserves of coal, but are short of other fossil fuels. Also, many large coal-fired power stations already exist and are expected to be still operating in 15 years time. The challenge faced by technologists and the business community is to reduce emissions of sulfur dioxide and nitrogen oxides from these existing plants within a competitive cost framework. High-sulfur coal will become of very little value unless a low-cost method is found to remove the sulfur before combustion, or for trapping the sulfur dioxide when released. At present, flue-gas desulfurization units (where fitted) impose a significant cost penalty on coal-fired power stations. Looking further ahead to a time when supplies of natural gas start to dwindle, the vast coal stocks will have to be used in an environmentally friendly fashion and therefore will require effective ‘clean coal’ technologies (see Section 2.3, Chapter 2).

It is equally important that methods for the sequestration of carbon dioxide be found. Underground storage or disposal in the sea, for example, would require new utilities to be built near suitable reservoirs or the coast, otherwise a transport system would have to be established for the conveyance of carbon dioxide, either by pipeline for the gas or by tanker for the liquefied form.

Gas-fired, combined-cycle, power stations are now preferred to those fueled by coal, on the grounds of both higher efficiency and lower emissions. The extent to which such plants can be introduced depends on many factors such as: the availability of gas supplies; fiscal considerations of the cost of importing gas (where necessary) rather than using indigenous coal; political issues where coalminers’ jobs are at stake; the matter of diversifying the fuel base of electricity to ensure security of supply. These factors will vary from nation to nation.

The growing dependence of Western Europe on natural gas imported from countries of the former USSR and from North Africa is a potential cause of concern. These sources involve very long transmission pipelines that carry massive quantities of gas and are open to disruption as a result of accident or sabotage. In the event of restricted gas supplies, the electricity industry would be the first to be rationed and priority would be accorded to domestic and commercial users. This would be decided on safety grounds. When gas supply is interrupted and taps are left open, air can back-diffuse into the line and lead to the possibility of an explosion. With millions of households this is a real danger, whereas professional users, such as electricity utilities, have safe shut-down procedures. The more dependent a nation is on imported gas for its electricity, obviously the more serious would be the consequences following the cessation of power due to a gas shortage. Constructing gas-storage facilities might mitigate short-term disruptions in supply. One example would be to re-inject Russian gas into depleted North Sea gas fields as a large-scale store. With the benefit of hindsight, a better option might have been not to deplete gaseous resources so quickly in the first place! The swing to gas-fired electricity plant has undoubted advantages in the short term, both economic and environmental, but may be storing up problems for the longer term.

Distributed generation should make a growing contribution to overall electricity supply during the next 20 years. Nevertheless, we suggest that distributed generation and electricity derived from renewables (excluding hydroelectricity, which is already well established) will still constitute only a minor component of the worldwide production of electricity.

Another growth area in electricity generation will be that of CHP. Obviously, it makes sense to utilize, where practical, the waste heat associated with electricity generation. The rate of growth of this sector will be determined by cost considerations and by the availability of a suitable market for the heat. Whereas the quantity of heat that is potentially available from a 1 to 2 GW power station is huge, the distance over which it can be conveyed is limited. Thus, district heating is only a practical proposition in situations where the station is adjacent to a city. Moreover, installing district heating in a city is both capital intensive and highly disruptive. Although the overall efficiency of a CHP plant (electricity+heat) is high, the requirement to operate with exhaust gases at a higher temperature results in a reduced efficiency for electricity generation. For all these reasons, it is likely that CHP installations will be confined to relatively small distributed systems and not to large central power stations. Similarly, stationary fuel cells, if they come to pass, will almost certainly be relatively small units.

By far the largest uncertainty lies in the future of the nuclear industry. Whether or not more nuclear stations will be approved and built is essentially a political question, that is unlikely to be resolved until there is a consensus on the reprocessing of nuclear fuel and how best to store radioactive waste indefinitely. With so much public opposition to nuclear power, despite its record of reliable and safe operation in many countries, it may be difficult for governments to approve the construction of further nuclear stations. This situation will certainly vary from country to country and will be determined by a given nation’s energy needs and resources, as well as the strength of public opinion. There is also the separate question of the large up-front capital cost and the long lead-times in constructing nuclear stations. Now that responsibility for electricity generation is moving from the public to the private sector in many countries, this may be a deterrent to further major investment. At present, then, the future of nuclear power is very uncertain, but by 2020 the issues should be resolved one way or the other and the industry will either be in terminal decline or in a growth phase where ageing plant is being replaced. The success (or otherwise) of the pebble-bed modular reactor (see Section 3.5, Chapter 3) may also be a pertinent factor. Countries that derive a high proportion of their electricity from nuclear sources (e. g. France) will have a particular problem when reactors reach the end of the their life and have to be replaced.

On the horizon, there is the prospect of generating electricity by nuclear fusion. Steady research progress is being made in major laboratories and the next significant step will most probably be a single world demonstration project. Not even the most optimistic of proponents, however, see this technology contributing to world electricity supplies by 2020.